[lldb] Fix Linux core file tests hanging on Windows

After #141670,
TestLinuxCore.py was timing out on our Windows on Arm bot.

Non-Linux core files were ok, as were Linux core files unless
it was ppc64le, riscv64 or loongarch.

I eventually noticed that it was attempting to create
PlatformLinux many times before trying PlatformAndroid,
PlatformMac etc., which it should never need to do.

The tests passed on a Linux host too, to add to the mystery.

Turns out, all I needed to do was mark those architectures
as supported in the PlatformLinux constructor.

If they're not listed there we get stuck here:
```
    // Wait for a stopped event since we just posted one above...
	printf("waiting for process to stop...\n");
    lldb::EventSP event_sp;
    StateType state =
        WaitForProcessToStop(std::nullopt, &event_sp, true, listener_sp,
                             nullptr, true, SelectMostRelevantFrame);
    printf("process stopped\n");
```
Waiting for a stop event that never comes, because it appears we
try to treat the core as a real process?
```
 DynamicLoaderPOSIXDYLD::virtual DynamicLoaderPOSIXDYLD::DidAttach pid 28147 executable '<null executable>', load_offset 0xffffffffffffffff
<...>
 Process::ShouldBroadcastEvent (000002ABC43FF4A0) Restarting process from state: stopped
 Process::PrivateResume() m_stop_id = 1, public state: unloaded private state: stopped
 Process::PrivateResume() got an error "error: elf-core does not support resuming processes".
 Process::ShouldBroadcastEvent (000002ABC43FF4A0) => new state: stopped, last broadcast state: invalid - NO
```

Some sort of actionable feedback here would be nice, but all I care
about for now is that the tests run again.

I have not added riscv32 as that appears to only be supported
for Darwin at the moment (though I expect someone will get
burned by this when it is).

I think debug on these architectures worked if they were also
the host arch, if someone tried to remote debug them, I think
it would fail.

Author: DavidSpickett

lldb/source/Plugins/Platform/Linux/PlatformLinux.cpp

@@ -138,7 +138,9 @@ PlatformLinux::PlatformLinux(bool is_host)
         {llvm::Triple::x86_64, llvm::Triple::x86, llvm::Triple::arm,
          llvm::Triple::aarch64, llvm::Triple::mips64, llvm::Triple::mips64,
          llvm::Triple::hexagon, llvm::Triple::mips, llvm::Triple::mips64el,
-         llvm::Triple::mipsel, llvm::Triple::msp430, llvm::Triple::systemz},
+         llvm::Triple::mipsel, llvm::Triple::msp430, llvm::Triple::systemz,
+         llvm::Triple::loongarch64, llvm::Triple::ppc64le,
+         llvm::Triple::riscv64},
         llvm::Triple::Linux);
   }
 }